Sheet-cutting apparatus

ABSTRACT

A sheet cutter for cutting a sheet with a cutting blade held by a cutting blade elevating body which is elevated by one servo motor, including a pair of cutting blade elevating bodies; an elevation driving body for elevating the pair of cutting blade elevating bodies; a guide member for guiding the elevation of the pair of cutting blade elevating bodies; a holding body capable of holding the pair of cutting blade elevating bodies at an up position; and a transmission change-over device for selectively engaging the pair of cutting blade elevating bodies with the elevation driving body and selectively disengaging the pair of cutting blade elevating bodies from the elevation driving body, wherein one of the pair of cutting blade elevating bodies, which has been selected, is elevated by the servo motor.

TECHNICAL FIELD

The present invention relates to a sheet cutter for conductingcomplete-cutting or half-cutting (cutting a sheet while leaving aportion of predetermined thickness of the sheet) on a soft sheet such asa ceramic green sheet. More particularly, the present invention relatesa sheet cutter provided with two or more cutting blades.

BACKGROUND ART

Concerning a conventional sheet cutter for cutting a soft sheet such asa ceramic green sheet, for example, sheet cutters which are disclosed inthe official gazettes of Japanese Unexamined Patent Publication Nos.2001-113520 and 1-122408 are known. Japanese Unexamined PatentPublication No. 2001-113520 discloses a sheet cutter having thefollowing cutting blade attaching structure. The sheet cutter has onecutting blade which is elevated by one drive section. A cutting bladeholder (cutting blade elevating body) to which the cutting blade isattached is fixed to a lower end portion of the guide rod, which iselevatably provided in the frame, in such a manner that the cuttingblade holder protrudes downward, and an elevating drive section isconnected to a center on an upper face of the cutting blade holder.

Japanese Unexamined Patent Publication No. 1-122408 discloses a sheetcutter having the following cutting blade attaching structure. A basetable is provided on a movable table elevated by a feed screw, and ahorn (cutting blade elevating body) is attached to the base table insuch a manner the horn protrudes downward and one cutting blade isattached to the horn.

As described above, as one cutting blade is elevated by one drivesection in the cutter described in Japanese Unexamined PatentPublication No. 2001-113520, in the case where a pair of cutting bladeelevating bodies are provided, it is necessary to provide a pair ofguide rods and it is also necessary to provide a pair of drive sections.Accordingly, problems may be caused in which the structure of thecutting blade elevating section becomes complicated and the size of thecutting blade elevating section is extended.

In addition, as a pair of guide rods are elevatably arranged in theframe and the cutting blade elevating body is attached to a lower endportion of the guide rod in such a manner that the cutting bladeelevating body protrudes downward, the cutting blade elevating body isliable to be deformed or tilted. Therefore, the cutting accuracy of thesheet cutter is lowered.

In the case of Japanese Unexamined Patent Publication No. 1-122408, thefollowing problems may be encountered. The base table is arranged on themovable table elevated by the feed screw, and the horn is attached tothe base table in such a manner that the horn protrudes downward. Thus,in the case where a pair of cutting blades are provided, it is necessaryto have a pair of feed screws and it is also necessary to have a pair ofmovable tables. Therefore, the structure becomes complicated and thesize of the sheet cutter is extended. Further, the horn to hold thecutting blade is liable to be tilted. Accordingly, the cutting accuracyis lowered.

The present invention has been accomplished to solve the above problemsof the prior art. It is an object of the present invention to provide asheet cutter in which the cutting blade elevating section is downsized;the cutting accuracy is high; and the cutting speed is increased, evenif the sheet cutter cuts a sheet, so as to have different cuttinglengths, with two cutting blades.

DISCLOSURE OF THE INVENTION

In order to solve the above problems, in the first embodiment, a sheetcutter for cutting sheet with a cutting blade held by a cutting bladeelevating body which is elevated being driven by one servo motor,comprises: a pair of cutting blade elevating bodies; an elevationdriving body for elevating the pair of cutting blade elevating bodies; aguide member for guiding the elevation of the pair of cutting bladeelevating bodies; a holding body capable of holding the pair of cuttingblade elevating bodies at a up position; and a transmission change-overdevice for selectively engaging the pair of cutting blade elevatingbodies with the elevation driving body and selectively disengaging thepair of cutting blade elevating bodies from the elevation driving body,wherein one of the pair of cutting blade elevating bodies, which hasbeen selected, is elevated by the servo motor.

According to the above constitution, a pair of cutting blade elevatingbodies are selectively elevated by the transmission change-over device.Therefore, even in the case of a sheet cutter in which a sheet can becut into a different cutting length with two cutting blades, forexample, a sheet can be cut into a rectangle when the sheet cutter isoperated being combined with a turn table, the pair of cutting bladeelevating bodies can be arranged close to each other and the device canbe downsized, and further the sheet cutter can be sufficiently operatedby only one cutting blade elevating device. Therefore, the structure canbe made simple. As the elevating motion of the cutting blade elevatingbody is guided by the guide member, the deformation and inclination ofthe cutting blade can be reduced.

According to the second embodiment, in the sheet cutter according to thefirst embodiment, through-holes communicating with each other in thehorizontal direction at a up position of the cutting blade elevatingbody are formed in both the elevation driving body and the pair ofcutting blade elevating bodies, and a transmission change-over device iscomposed which includes a connecting pin inserted into the through-holesand also includes a pin change-over moving device for selectively movingthe connecting pin between a position where the connecting pin isinserted into the through-hole of the elevation driving body and intothe through-hole of one of the cutting blade elevating bodies in abridge-like state and other position where the connecting pin isinserted into the through-holes of the elevation driving body and notinserted into the through-holes of one of the cutting blade elevatingbodies in a non-bridge-like state. Due to the above constitution, thecutting blade elevating body to be elevated can be accurately andpositively changed over.

According to the third embodiment, in the first embodiment, a pair ofhorizontal through-holes are formed in the elevation driving body, aholding member is stationarily provided on one side of the through-holedirection of the elevation driving body at a up position, one of thecutting blade elevating bodies is partially inserted between the holdingmember and the elevation driving body, the holding member isstationarily provided on the other side in the through-hole direction ofthe elevation driving body, the other cutting blade elevating body ispartially inserted between the holding member and the elevation drivingbody, the through-hole opposed to one of the through-holes formed in theelevation driving body is respectively provided in the holding memberand the cutting blade elevating body on one side, the through-holeopposed to the other through-hole formed in the elevation driving bodyis respectively formed in the holding member and the cutting bladeelevating body on the other side, and a transmission change-over deviceis composed which includes a pair of connecting pins inserted into twosets of through-holes opposed to each other and also includes a pinchange-over moving device capable of being selectively moved between aposition, at which one of the connecting pins functions as a bridgebetween the through-holes of the elevation driving body and the cuttingblade elevating body and further the other connecting pin is disengagedfrom the elevation driving body and functions as a bridge between thethrough-holes of the holding body and the cutting blade elevating body,and a position at which one of the connecting pins is disengaged fromthe elevation driving body and functions as a bridge between thethrough-holes of the holding member and the cutting blade elevating bodyand the other connecting pin functions as a bridge between thethrough-holes of the elevation driving body and the cutting bladeelevating body. Due to the above constitution, a connection of theelevation driving body with the pair of cutting blade elevating bodiescan be accurately and positively executed by a simple structure.

According to the fourth embodiment, in the second or the thirdembodiment, a pushing pawl capable of pushing upward one of the cuttingblade elevating body and the elevation driving body under the conditionthat both are connected to each other is provided in the other, and acontacting member capable of releasing the pushing action by the pushingpawl at a up position of the elevation driving body is provided. Due tothe above structure, it is possible to eliminate a gap in the verticaldirection between the cutting blade elevating body and the elevationdriving body under the connecting condition. Therefore, it is possibleto highly accurately position a lower position of the cutting bladeelevating body. Accordingly, half-cutting can be highly accuratelyconducted on a sheet. Further, a change-over can be smoothly conductedbetween the connection with the cutting blade elevating body and theconnection with the elevation driving body.

According to the fifth embodiment, in one of the first to the fourthembodiment, the guide member includes a pair of guide rails arranged atthe right and left end portions of the cutting blade elevating body inparallel to the cutting blade elevating direction and also includes apair of guide pieces vertically arranged in the corresponding sheetcutter frame, and the guide rail can be slidably moved on the guidepiece. Due to the above structure, both the distance between the cuttingblade and the guide member in the vertical direction and the distancebetween the cutting blade and the guide member in the horizontaldirection can be reduced, and the deformation and inclination of thecutting blade can be decreased. Therefore, the cutting blade elevatingbody can be smoothly elevated at high speed while its posture is beingstably maintained. Accordingly, cutting operation can be conducted athigh speed while the cutting accuracy is being maintained high.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration showing an embodiment of the sheetcutter of the present invention, that is, FIG. 1 is a schematicillustration showing a cutting blade elevating section which is aprimary portion of the sheet cutter of the present invention;

FIG. 2 is a sectional schematic illustration taken on line A-A in FIG.1;

FIG. 3 is a sectional schematic illustration taken on line B-B in FIG.1;

FIG. 4 is a sectional schematic illustration taken on line C-C in FIG.1;

FIG. 5 is a sectional schematic illustration taken on line D-D in FIG.1;

FIG. 6 is a front schematic illustration showing a sheet cutter providedwith the cutting blade elevating section shown in FIG. 1; and

FIG. 7 is a schematic illustration showing the left face of FIG. 6.

MOST PREFERRED EMBODIMENT

Referring to the accompanying drawings, an embodiment of the presentinvention will be explained below in detail. FIGS. 1 to 5 are viewsshowing an embodiment of the sheet cutter of the present invention, thatis, FIGS. 1 to 5 are schematic illustrations showing a cutting bladeelevating section which is a portion of the sheet cutter. FIG. 1 is afront view, FIG. 2 is a sectional view taken on line A-A, FIG. 3 is asectional view taken on line B-B, FIG. 4 is a sectional view taken online C-C, and FIG. 5 is a sectional view taken on line D-D. In FIG. 1,reference numeral 1 is a cutting blade, and reference numeral 2 is acutting blade elevating body. The cutting blade 1 is exchangeablyattached to the cutting blade fixture 1 a which is removably attached tothe cutting blade elevating body 2. Reference numeral 3 is a servo motorfor elevating the cutting blade elevating body 2, and reference numeral4 is a frame of the sheet cutter.

In this connection, reference numeral 7 is a work setting base on whicha work to be cut is set. The work setting base 7 is arranged on themovable base 52, which is guided by the guide rail 51 so that it can bemoved forward, and is capable of revolving by the angle of 90°.Reference numeral 8 is a motor for moving the movable base 52 in theback-and-forth direction. Reference numeral 9 is a cleaning utensilmoving device for moving a cleaning utensil 9 a used for cleaning thecutting blade 1 .

As shown in FIGS. 2 and 5, a pair of cutting blade elevating bodies 2are provided in such a manner that the plate-shaped frame 4 a, which isvertically arranged at the center, is interposed between the pair ofcutting blade elevating bodies 2. At the central upper portion of thepair of cutting blade elevating bodies 2, 2, one elevation driving body10 is arranged in such a manner that the elevation driving body 10 canbe elevated by the screw shaft 11. The cutting blade elevating bodies 2are selectively engaged with and disengaged from the elevation drivingbody 10 by a transmission change-over device Q described later.Therefore, one of the cutting blade elevating bodies 2 is connected tothe screw shaft 11 via the elevation driving body 10. As shown in FIGS.1 to 3, the feed screw shaft 11 is screwed to the nut 56 which ispivotally supported by the holding body 55 fixed to the support shaft 54integrated with the frame 4. This nut 56 is normally rotated andreversed by the servo motor 3, which is arranged at an upper portion ofthe frame 4, via the belt 12 and the pulley 57. As a result of therotation of the nut 56, the cutting blade elevating body 2 connected tothe elevation driving body 10 is elevated when the cutting bladeelevating body 2 is driven by the servo motor 3. In this connection, theother cutting blade elevating body 2 not connected to the elevationdriving body 10 is stationarily fixed to a up position meanwhile by theholding member described later. It is also possible to rotate the feedscrew 11 by the servo motor 3 and elevate the elevation driving body 10by the nut 56.

Next, explanations will be made regarding the transmission change-overdevice Q which selectively engages the pair of cutting blade elevatingbodies 2 with the elevation driving body 10 and also selectivelydisengages the pair of cutting blade elevating bodies 2 from theelevation driving body 10. As shown in FIG. 4, the elevation drivingbody 10 is connected to a lower portion of the feed screw shaft 11. Inan upper portion of the pair of cutting blade elevating body 2, theengaging pieces 13 respectively engaging with the elevation driving body10 are arranged and formed into a U-shape in such a manner that theengaging pieces 13 surround an end portion of the elevation driving body10. The engaging pieces 13 may be formed and integrated with the cuttingblade elevating body 2. Alternatively, as shown in the drawing, theengaging pieces 13 may be formed separate from the cutting bladeelevating body 2 and fixed to the cutting blade elevating body 2. Theseengaging pieces 13 are composed in such a manner that the engagingpieces 13 a of the front side cutting blade elevating body 2 and theengaging pieces 13 b of the rear side cutting blade elevating body 2 arearranged in the front and the rear of the elevation driving body 10 andopposed to each other.

In the right and left end portions of the engaging pieces 13 a, 13 bsurrounding the elevation driving body 10, the through-holes 14 a, 14 aare formed in the side to side direction in such a manner that thethrough-holes 14 a, 14 a respectively penetrate the elevation drivingbody 10. In the same manner, in the elevation driving body 10, twothrough-holes 14 b, 14 b are respectively formed which are opposed tothe through-holes 14 a, 14 a of the engaging pieces 13 a, 13 b at apredetermined up position. The connecting pins 15 capable of beinginserted into the through-holes 14 b, 14 b of the elevation driving body10 are respectively inserted into the through-holes 14 a, 14 a of theengaging pieces 13 a, 13 b. The annular engaging grooves 60 used forpositioning are formed in both end portions of the connecting pins 15.These annular engaging grooves 60 are engaged with the notch pins 61embedded in the engaging pieces 13 a so as to be positioned, that is, soas to prevent the connecting pins 15 from coming out.

As shown in FIG. 4, in an upper portion of the frame 4 located on theright and left of the cutting blade elevating body 2, the cylinders 18,18 are arranged with piston rods which extend and retract in the lateraldirection being opposed to each other, and have guide rods. Therod-shaped push-out pins 17 a and the push-in pins 17 b are arranged atthe forward end portions of the piston rods in such a manner that thepush-out pins 17 a and the push-in pins 17 b are alternately opposed toeach other. The push-out pins 17 a and the push-in pins 17 b arearranged so that they have the same axes as the through-holes 14 a ofthe engaging pieces 13, 13 at the up position of the cutting bladeelevating body 2. The push-out pins 17 a and the push-in pins 17 b areformed in such a manner that the diameters of these pins are smallerthan the diameters of the connecting pins 15.

A pair of holding means 19 are provided between the cylinders 18, 18 andthe engaging pieces 13, 13. A pair of front and rear through-holes 19 a,19 a, into which the push-out pins 17 a, the push-in pins 17 b and theconnecting pins 15 can be inserted, are formed in the holding means 19.As shown in FIG. 1, the pair of holding members 19 are fixed onto theframe 4. In this connection, the cylinder 18 is operated by pneumaticpressure, however, the cylinder 18 may be operated by an electric motor.Both cylinders 18, 18 are composed as follows. The push-out pins 17 aare longer than the push-in pins 17 b. The push-in pins 17 b arearranged being opposed to the push-out pins 17 a. When the piston rod isprotruded, the push-out pins 17 a push out the connecting pins 15 fromthe through-holes 14 b of the elevation driving body 10. Therefore, thepush-in pins 17 b push in the connecting pins 15 to positions where theconnecting pins 15 act as a bridge between the through-holes 14 b of theelevation driving body 10 and the through-holes 14 a of the engagingpieces 13.

Transmission change-over device Q includes the engaging pieces 13 of theelevation driving body 10, the connecting pins 15, the push-out pins 17a, the push-in pins 17 b and the holding member 19 which are composed asdescribed above. This transmission change-over device Q is operated asfollows. When one of the cylinders 18 is operated and the push-out pin17 a is protruded at the time of a rise of the cutting blade elevatingbody 2, the connecting pin 15 collides with the push-out pin 17 a and ispushed out to the push-in pin 17 b side opposed to the push-out pin 17a. Due to this movement, the engaging pieces 13 connected to theelevation driving body 10 by the connecting pins 15 are released fromthe elevation driving body 10 and engaged and connected with the holdingbody 19. This state is held by the engagement of the engaging grooves 60with the notch pins 61. As a result, one cutting blade elevating body 2including the engaging pieces 13 connected to the holding member 19 isnot elevated and is reliably held in the fixed state at the up position.

The push-in pins 17 b push in the connecting pins 15, which are insertedinto the through-holes 19 a of the holding member 19, in such a mannerthat the connecting pins 15 act as a bridge between the through-holes 14b of the elevation driving body 10 and the through-holes 14 a of theengaging pieces 13. This state is held by the engagement of the engaginggrooves 60 with the notch pins 61. Accordingly, the other cutting bladeelevating body 2 is connected to the elevation driving body 10.

When the other cylinder 18 is operated in this state and the push-inpins 17 b, which are arranged being opposed, are protruded, theconnecting pins 15, which have been pushed out, are pushed back, and theengaging pieces 13 and the holding member 19 are released from eachother, and the connecting pins 15 penetrate the elevation driving body10. Therefore, the engaging pieces 13 are connected to the elevationdriving body 10 again. The push-out pins 17 a push out the connectingpins 15 from the through-holes 14 b of the elevation driving body 10 andinsert them into the through-holes 19 a of the holding member 19. Inthis way, the device returns to the initial state. Therefore, one of thecutting blade elevating body 2 can be elevated, and the other cuttingblade elevating body 2 is held without being elevated. As describedabove, the cylinder 18 provided with the push-out pins 17 a and thepush-in pins 17 b compose the pin change-over device.

Next, as shown in FIGS. 1 and 2, in the vicinity of the center of theside on the front and rear of the cutting blade elevating body 2, thebracket 65 is fixed, and a pair of spring support rods 66, risingupward, are fixed to this bracket 65. As shown in FIG. 1, these springsupport rods 66 penetrate the holes formed in the spring receivingmember 68 which is arranged at a lower end portion of the support member67 fixed to the support frame 54 hung downward. The compressive spring70 is interposed between the spring receiving seat 69, which is providedin an upper end portion of the spring support rod 66, and the springreceiving member 68, and a spring force generated by the compressivespring 70 acts upward on the cutting blade elevating body 2 via thespring support rod 66. Accordingly, the weight of the cutting bladeelevating body 2 can be balanced with the spring force of thecompressive spring 70. Therefore, an elevation of the cutting bladeelevating body 2 can be smoothly conducted by a low intensity of forcegenerated by the rotation of the nut 56 at high speed.

As shown in FIG. 2, at upper end portions of the engaging pieces 13, thepushing pawls 75 capable of pushing an upper face of the elevationdriving body 10 are attached round the axes 76 so that the pushing pawls75 can be pivoted upward and downward. The pushing fixtures 77, whichare comprised of springs and pushing pins, are interposed between thereceiving pieces 75 a on the lower end side of the pushing pawls 75 andthe engaging pieces 13. By the spring forces of these pushing fixtures77, the pushing pieces 75 b on the upper end side come into contact withan upper face of the elevation driving body 10 and push the elevationdriving body 10 downward. The receiving pieces 75 a of the pushing pawls75 come into contact with the contacting members 79, which are fixed atan intermediate portion of the support member 67 when the cutting bladeelevating body 2 is moved to the up position. Therefore, the pushingfixtures 77 are rotated in the direction of compression, and the pushingpieces 75 b on the upper end side are separated from an upper face ofthe elevation driving body 10, and a pushing action of the elevationdriving body 10 is temporarily released. Accordingly, in the case wherethe cutting blade elevating body 2 is moved to the up position and aconnection of the pair of cutting blade elevating bodies 2 with theelevation driving body 10 is changed over, the pushing motion of thepushing pawls 75 to push the elevation driving body 10 is released.Therefore, the connecting pins 15 can be smoothly changed over by a lowintensity of force. In the case where the cutting blade elevating body 2is elevated by the elevation of the elevation driving body 10, a gap(play) in the vertical direction in the connecting portion of theelevation driving body 10 with the cutting blade elevating body 2 iseliminated, so that a lowering position of the cutting blade elevatingbody 2 can be highly accurately positioned. As a result, half-cutting,in which a portion of a sheet corresponding to a predetermined thicknessis left uncut, can be highly accurately and uniformly conducted.

In this connection, in FIG. 2, the pushing pawls 75 are provided in thecutting blade elevating body 2, however, the pushing pawls 75 may beprovided in the elevation driving body 10 so that the pushing pawls 75can push the cutting blade elevating body 2 upward. For example, thefollowing structure may be employed. In FIG. 2, the elevation drivingbody 10 is formed in such a manner that the elevation driving body 10 isextended downward, and the frame 4 a is cut away so as to ensure aspace. Then, the pushing pawls 75 are attached to a lower end portion ofthe elevation driving body 10 in a direction being rotated by the angle180°, and a portion of the cutting blade elevating body 2 is pushedupward by the pushing pieces 75 b of the pushing pawls 75. That is, theabove object can be accomplished in the following manner. The pushingpawls 75 are provided in one of the cutting blade elevating body 2 andthe elevation driving body 10 so that the other can be pushed upwardunder the condition that both are connected to each other, and thecontacting member is provided in the frame, by which the pushing actionof the pushing pawls 75 can be released at the up position of thecutting blade elevating body 2 and the elevation driving body 10.

Referring to FIG. 4, the action of the cutting blade elevating sectioncomposed as described above will be explained below in more detail. InFIG. 4, the cutting blade elevating body 2 on the upper side in thedrawing, that is, the cutting blade elevating body 2 on the rear side isconnected to the elevation driving body 10 so that it can be elevated,the cutting blade elevating body 2 on the front side is held at a fixedposition. Explanations will be made below with the reference numeralsdefined as follows. Reference numeral 13 a denotes a front side engagingpiece 13 a, reference numeral 13 b denotes a rear side engaging piece,reference numeral 15 a denotes a front side connecting pin, referencenumeral 15 b denotes a rear side connecting pin, reference numeral 18 adenotes a left cylinder, and reference numeral 18 b denotes a rightcylinder.

As the rear side engaging piece 13 b is connected to the elevationdriving body 10 by the rear side connecting pin 15 b, the rear sideengaging piece 13 b is directly elevated by the feed screw shaft 11. Onthe other hand, the front side engaging piece 13 a is connected to theholding member 19 by the front side connecting pin 15 a and notconnected to the elevation driving body 10. Therefore, the front sideengaging piece 13 a is fixed to the holding member 19 side, that is, thefront side engaging piece 13 a is fixed to the frame 4 side.Accordingly, the front side engaging piece 13 a is not elevated.

In the above state, the change-over operation can be conducted asfollows. When the push-out pin 17 a of the right cylinder 18 b isprotruded, the rear side connecting pin 15 b is moved, and the rear sideengaging piece 13 b is released from the elevation driving body 10 andthe connecting pin 15 b is connected to the left holding member 19. Atthe same time, when the push-out pin 17 b of the right cylinder 18 b isprotruded, the front side connecting pin 15 a is moved and the frontside engaging piece 13 a is released from the holding member 19 of thefront side engaging piece 13 a. Therefore, the front side connecting pin15 a is connected to the elevation driving body 10. In this way, it ispossible to obtain a state in which the state shown in FIG. 4 is changedover. That is, it is possible to obtain a state in which the front sidecutting blade elevating body 2 is elevated and the rear side cuttingblade elevating body 2 is held at the fixed position.

As described above, a pair of cutting blade elevating bodies 2, 2 can beselectively elevated by transmission change-over device Q. Therefore,even in the case of a sheet cutter capable of cutting a sheet into arectangle by using two cutting blades, when the sheet cutter is combinedwith a work setting base, which can be revolved, a pair of cutting bladeelevating bodies can be arranged close to each other. Therefore, thedevice can be downsized. Further, the cutting blade can be easilyexchanged, and only one servo motor is sufficient for elevating thecutting blade, that is, the structure of the sheet cutter can be madesimple.

In the right and the left end portion of the cutting blade elevatingbody 2, the guide rails 23, which extend in the vertical direction inparallel to each other, are attached all over the length. To the frame 4opposed to the guide rails 23, the long guide piece 24 composing arectilinear motion guide device is fixed. As shown in FIGS. 4 and 5, theguide rails 23 are provided so that the cutting blade elevating body 2can be slid being engaged with the guide pieces 24 when the cuttingblade elevating body 2 is elevated. Therefore, the cutting bladeelevating body 2 can be stably elevated.

As described above, the elevating motion of the cutting blade elevatingbody is guided on both sides of the cutting blade elevating body 2 bythe guide members composed of the guide rails 23 and the guide pieces24. Therefore, the distances between the cutting blade 1 and the guidemember in the vertical and the horizontal directions can be reduced.Accordingly, it is possible to reduce a deformation and inclination ofthe cutting blade. Further, it becomes possible to conduct cuttingoperation with high accuracy at high speed. As the cutting bladeelevating body is slid in the vertical direction being guided by theguide pieces 24, the cutting blade elevating body to be elevated can beaccurately, positively changed over. Therefore, while the cuttingaccuracy is being maintained high, the cutting blade elevating body canbe smoothly elevated at high speed.

FIGS. 6 and 7 are overall arrangement views of the sheet cutter providedwith the above cutting blade elevating section. FIG. 6 is a frontschematic illustration, and FIG. 7 is a schematic illustration showingthe left face. Reference numeral 5 is a cutting blade elevating section.As shown in the drawing, the cutting blade elevating section 5 islocated at the substantial center of the device. As shown in FIG. 6, thework setting base 7 is assembled to the moving base 52 which moves inthe side to side direction and is capable of revolving through an angleof 90°.

As described above in detail, according to the present invention, a pairof cutting blade elevating bodies are selectively elevated by thetransmission change-over device. Therefore, even in the case of a sheetcutter in which a sheet can be cut into a different cutting length withtwo cutting blades, the pair of cutting blade elevating bodies can bearranged close to each other and the device can be downsized, and thecutting blades can be easily replaced and, further, the sheet cutter canbe sufficiently operated by only one cutting blade elevating device.Therefore, the structure can be made simple.

Through-holes are provided in both the elevation driving body and thepair of cutting blade elevating bodies, and a transmission change-overdevice is composed in such a manner that the pin change-over movingdevice selectively moves the connecting pin, which is inserted intothese through-holes, between a bridge state, in which the connecting pinacts as a bridge between the through-hole of the elevation driving bodyand the through-hole of one of the cutting blade elevating bodies, andno bridge state in which the connecting pin does not act as a bridgebetween the through-hole of the elevation driving body and thethrough-hole of one of the cutting blade elevating bodies. Therefore,the connection of the elevation driving body with the pair of cuttingblade elevating body can be accurately and positively changed over by asimple structure.

A pair of through-holes are provided in the elevation driving body. Onboth sides of the elevation driving body, the holding member isstationarily arranged, and the corresponding cutting blade elevatingbody is partially inserted into between them. Through-holes opposed tothe corresponding through-holes of the elevation driving body areprovided in the holding member and the cutting blade elevating body. Theconnecting pin inserted into the through-holes can be selectively moved,by the pin change-over device between a position of bridge in which theconnecting pin acts as a bridge between the through-hole of theelevation driving body and the through-hole of the cutting bladeelevating body and a position of bridge in which the connecting pin actsas a bridge between the through-hole of the holding member and thethrough-hole of the cutting blade elevating body. In this way, thetransmission change-over device is composed. Therefore, the cuttingblade elevating body released from the connection with the elevationdriving body can be positively held at the up position by a simplestructure. Accordingly, the change-over motion to change over theconnection can be positively conducted.

Further, a pushing pawl capable of pushing upward one of the cuttingblade elevating body and the elevation driving body under the conditionthat both are connected to each other is provided in the other of thecutting blade elevating body and the elevation driving body, and acontacting member capable of releasing the pushing action by the pushingpawl at a up position of the elevation driving body is provided.Therefore, it is possible to eliminate a gap in the vertical directionin the connecting section between the cutting blade elevating body andthe elevation driving body in the state of connection. Therefore, alowering position of the cutting blade elevating body can be highlyaccurately positioned, and half-cutting can be highly accuratelyconducted on a sheet. Further, the connection with one of the cuttingblade elevating bodies and the elevation driving body can be smoothlychanged over.

Further, the elevation of the cutting blade elevating body is guided onboth sides of the cutting blade elevating body by the guide member.Therefore, the distance between the cutting blade and the guide membercan be reduced, and it is possible to decrease a deformation andinclination of the cutting blade. Accordingly, it is possible to highlyaccurately cut a sheet at high speed.

1. A sheet cutter for cutting a sheet with a cutting blade held by acutting blade elevating body which is elevated by one servo motor,comprising: a pair of cutting blade elevating bodies; an elevationdriving body for elevating the pair of cutting blade elevating bodies; aguide member for guiding the elevation of the pair of cutting bladeelevating bodies; a holding body capable of holding the pair of cuttingblade elevating bodies at an up position; and a transmission change-overdevice for selectively engaging the pair of cutting blade elevatingbodies with the elevation driving body and selectively disengaging thepair of cutting blade elevating bodies from the elevation driving body,wherein one of the pair of cutting blade elevating bodies, which hasbeen selected, is elevated by the servo motor, and wherein thetransmission change-over device comprises through-holes communicatingwith each other in the horizontal direction at an up position of thecutting blade elevating body that are formed in both the elevationdriving body and the pair of cutting blade elevating bodies, aconnecting pin to be inserted into the through-holes and a pinchange-over moving device for selectively moving the connecting pinbetween a position where the connecting pin is inserted into thethrough-hole of the elevation driving body and into the through-hole ofone of the cutting blade elevating bodies and a position where theconnecting pin is inserted into the through-holes of the elevationdriving body and not inserted into the through-holes of one of thecutting blade elevating bodies.
 2. The sheet cutter according to claim1, wherein each of the cutting blade elevating bodies includes a pushingpawl capable of pushing the elevation driving body downward, and whereinthe sheet cutter includes a contacting member capable of releasing thepushing action of the pushing pawl when the one of the cutting bladeelevating bodies is moved to an up position.